a. Field of the Invention
The instant disclosure relates generally to electrode support structure assemblies. In particular, the instant disclosure relates to electrode support structure assemblies for basket catheters including a plurality of splines.
b. Background Art
Electrophysiology catheters are used in a variety of diagnostic, therapeutic, and/or mapping and ablative procedures to diagnose and/or correct conditions such as atrial arrhythmias, including for example, ectopic atrial tachycardia, atrial fibrillation, and atrial flutter. Arrhythmias can create a variety of conditions including irregular heart rates, loss of synchronous atrioventricular contractions and stasis of blood flow in a chamber of a heart which can lead to a variety of symptomatic and asymptomatic ailments and even death.
Typically, a catheter is deployed and manipulated through a patient's vasculature to the intended site, for example, a site within a patient's heart or a chamber or vein thereof. The catheter carries one or more electrodes that can be used for cardiac mapping or diagnosis, ablation and/or other therapy delivery modes, or both, for example. Once at the intended site, treatment can include, for example, radio frequency (RF) ablation, cryoablation, laser ablation, chemical ablation, high-intensity focused ultrasound-based ablation, microwave ablation, and/or other ablation treatments. The catheter imparts ablative energy to cardiac tissue to create one or more lesions in the cardiac tissue and oftentimes a contiguous or linear and transmural lesion. This lesion disrupts undesirable cardiac activation pathways and thereby limits, corrals, or prevents errant conduction signals that can form the basis for arrhythmias.
Various catheters and electrode arrangements can be employed for different purposes. Catheters having basket-shaped electrode support structures are known and described in, for example and without limitation, U.S. Pat. No. 5,772,590 entitled “Cardiovascular Catheter with Laterally Stable Basket-Shaped Electrode Array with Puller Wire,” the entire disclosure of which is incorporated herein by reference as though set forth in its entirety. Generally, catheters having basket-shaped electrode support structures are introduced through a guiding sheath with the electrode support structure in a folded or collapsed position within the sheath so that the electrode support structure does not damage tissue during its introduction. Once the catheter reaches its intended position within the heart, the guiding sheath can be removed and the electrode support structure can be allowed to radially outwardly expand for cardiac mapping or diagnosis, ablation and/or other therapy delivery modes, or both, for example.
Typically, basket-shaped electrode support structures comprise a plurality of splines that can be formed from laser cut tubing and be integral at one end or that comprise discrete, separate elements. The distal ends of each of these plurality of splines generally must be joined together. For example, the distal ends of each of the plurality of splines can be mounted around a first piece of tubing and then be held in place by a second piece of tubing as generally described and illustrated in U.S. Patent Application Publication No. 2007/0276212 entitled “Basket Catheter With Improved Expansion Mechanism,” the entire disclosure of which is hereby incorporated by reference as though set forth in its entirety.
It is desirable for each of the splines to be joined in such a way that the splines are configured to straighten evenly when the electrode support structure is collapsed. However, it may be difficult for the electrode support structure to collapse evenly if manufacturing variances have resulted in differences in the individual lengths of the splines. It may also be difficult for the electrode support structure to collapse evenly if one or more of the splines have experienced a change in length relative to the remainder of the splines, such as during manipulation of the electrode support structure around a curve, for example. If the splines do not straighten evenly when the electrode support structure is collapsed, a protrusion or “loop” can form at the distal end of one or more of the plurality of splines. Continued collapse or multiple collapses of the electrode support structure can potentially cause fatigue at the point of the protrusion or “loop” and ultimately fracture the spline. Moreover, when the distal ends of the splines are fixed in place (e.g., mounted between two pieces of tubing), the distal flexibility of the splines may be limited, thereby adversely impacting the collapsibility of the electrode support structure. In addition, stress imparted at the distal end of the electrode support structure during collapse and/or expansion of the electrode support structure can also result in the failure of any strut or other element that may be configured to join the distal ends of the splines together.
Additionally, when the electrode support structure is in an expanded state, electrode distribution may not be uniform in accordance with some electrode arrangements. Moreover, during collapse of the electrode support structure (e.g., when the electrode support structure is emerging from or being retracted into a delivery sheath), some electrode arrangements may possibly result in electrode to electrode contact and/or short circuits, which may cause electrode wear and/or limit electrode functionality. In addition, some electrode arrangements may not minimize the profile of the electrode support structure during collapse of the electrode support structure, which can result in electrode damage when the electrode support structure is being delivered through the delivery sheath, especially when being delivered through a tortuously angulated pathway.
Typically, basket-shaped electrode support structures can include an expander having a distal end attached to a distal end of the electrode support structure. The expander includes a proximal end that extends out of a proximal end of a catheter or other medical device employing the electrode support structure to a control handle. The expander can be moved longitudinally relative to the catheter or other medical device to expand and contract the electrode support structure. The expander is generally coaxial with the catheter. An expander will not generally allow for free axial movement of the electrode support structure if the electrode support structure is being diametrically constrained in some way.
There is therefore a need to minimize and/or eliminate one or more of the problems as set forth above. The foregoing discussion is intended only to illustrate the present field and should not be taken as a disavowal of claim scope.